Simulated Blood Pressure Responses in Lie-Detector Tests and a Method for Their Detection

Reid's 1945 study identified that examinees could deliberately manipulate blood pressure responses during polygraph tests through covert muscular tension in the arms, legs, and thighs. He developed and patented an auxiliary detection system using metal bellows integrated into a specialized polygraph chair to detect these countermeasure attempts in real-time.

Observational case study documenting simulated blood pressure responses produced by deliberate muscular activity, followed by development and testing of a bellows-based auxiliary sensor system integrated into polygraph chair armrests and seat.

Background & Context

John E. Reid's 1945 publication represents one of the first scientific investigations into polygraph countermeasures, marking a pivotal moment in the evolution of deception detection technology. Working at the Chicago Police Scientific Crime Detection Laboratory, Reid confronted a fundamental vulnerability in early polygraph testing: examinees could deliberately manipulate their physiological responses through covert muscular activity.

This research emerged during a critical period in polygraph history. Reid developed a device which recorded muscular activity accompanying changes in blood pressure in 1945, addressing the roughly 20% of cases where results obtained were not acceptable using traditional blood pressure-pulse-respiration recording alone. The work preceded Reid's later fame for developing the Control Question Technique and established his reputation as an innovator in forensic psychophysiology.

Research Design & Methodology

Reid's investigation focused on identifying and detecting "simulated blood pressure responses"—artificially induced cardiovascular changes that could confound traditional polygraph measurements. Reid found that by various forms of unobserved muscular activity a subject's blood pressure could be changed in such a manner as to seriously affect the accuracy of the examiner's diagnosis.

The researcher documented specific countermeasure techniques through systematic observation and chart analysis:

• Muscular tension in the right arm caused a rise in the cardio tracing
• Blood pressure rise induced by an examinee pressing his feet to the floor
• Covert tensing of thigh and forearm muscles during critical questions

Reid's work led him to develop a device to detect such countermeasure efforts and to incorporate it into the polygraph instruments he had specially manufactured by the Stoelting company. The detection apparatus utilized metal bellows integrated into the armrests and seat of what became known as the "printing chair" or polygraph chair.

Results & Key Findings

Reid demonstrated that deceptive examinees could successfully distort blood pressure readings through deliberate muscular countermeasures, threatening the validity of cardiovascular-based lie detection. The research provided photographic evidence showing simulated blood pressure changes that mimicked genuine deception-related responses.

Key discoveries included:

• Countermeasure mechanisms: Arm tensing, leg pressing, and thigh muscle contraction could artificially elevate blood pressure readings
• Detection solution: Auxiliary muscular activity sensors could identify these covert manipulations in real-time
• Instrumentation breakthrough: Reid devised and invented the "Reid Polygraph" for recording muscular activity along with changes in blood pressure, pulse, respiration, and psychogalvanic skin reflex

The patent application filed November 19, 1945 detailed inflatable elastic bags for the thigh and forearms that transmitted pressure changes to recording tambours. This created an additional physiological channel specifically designed for countermeasure detection—a concept that remains relevant in modern polygraph practice.

Discussion & Significance

Reid's work represented a fundamental shift in polygraph theory: from assuming physiological responses were involuntary and uncontrollable to recognizing that sophisticated examinees could employ deliberate strategies to defeat testing. Reid advised Leonard Keeler of the article on countermeasures and desired to let other examiners know of his concern regarding examinees' distortion of test results.

The research established several enduring principles in psychophysiological detection of deception. Identifying countermeasures is a critical part of a competent examiner's training, with almost 25% of guilty suspects identified primarily because of their use of countermeasures in modern practice. Reid's auxiliary sensor approach anticipated contemporary motion detection systems, including activity pads in polygraph chairs that remain standard equipment today.

The 1945 paper also influenced Reid's subsequent theoretical development. His realization that examinees actively attempted to manipulate responses likely contributed to his later emphasis on psychological questioning techniques (the Control Question Technique) rather than relying solely on instrumentation to differentiate truth from deception.

Limitations & Considerations

The study's primary limitation was its descriptive rather than empirical approach—Reid demonstrated that countermeasures existed and could be detected, but did not provide systematic accuracy statistics or controlled experimental validation. The research appears based on case observations and instrumentation testing rather than controlled laboratory conditions with known ground truth.

Additionally, publishing countermeasure information created the classic "disclosure paradox" in polygraph science: educating examiners about detection methods simultaneously educated potential examinees about evasion techniques. The paper's illustrations showing exactly how to simulate blood pressure responses could serve as an instruction manual for sophisticated subjects.

The bellows-based detection system, while innovative for 1945, had sensitivity limitations compared to modern electronic motion sensors. None of the software developed for computer-analyzed charts is capable of identifying specific subject countermeasures, suggesting that even advanced technology has not fully solved the detection challenge Reid first identified.

Practical Applications

Reid's research established countermeasure detection as an essential component of competent polygraph examination. The use of Reid's device was a standard practice in the testing done by him and his colleagues, and modern polygraph chairs continue to incorporate activity sensors based on Reid's original concept. The chair enables examiners to closely monitor the test subject's movements and detect any movement that could affect physiological responses, crucial for identifying attempts to counteract the polygraph.

For examiners, the work underscores that chart interpretation must include vigilance for artifact and deliberate distortion. For consumers and policymakers, it provides early scientific documentation that polygraph tests are potentially vulnerable to informed countermeasures—a finding that remains central to debates about polygraph validity and admissibility seven decades later.